Lake Superior Mirage

April 08, 2011

Photographer: Randy Lane
Summary Author: Randy Lane; Jim Foster

The photo above appears to show a space-ship like object hovering above the sea. It's actually an inferior mirage of a lake freighter on Lake Superior. These immense ships are sometimes over 1,000 ft (300 m) long. This one is likely 16 mi (26 km) distant, which is the approximate distance from shore to the shipping lanes. I took the picture from Two Harbors, Minnesota on October 21, 2010 with the camera facing east. The air temperature at the time (7:20 a.m.) was about 35 degrees F (2 C), and the water temperature was perhaps 20 degrees F (11 C) warmer. Though the ship is displaced above its original position, it's not distorted. Thus, it's likely that the temperature gradient is rather uniform from the water surface to about 30 ft (~10 m) above the surface. 

With an inferior mirage, an object looks lower than its true position -- the index of refraction decreases rapidly toward the surface. Light refracts toward the more dense medium. 

Photo Details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D80; Lens: 70.0-300.0 mm f/4.0-5.6; Focal Length: 300.0mm (35mm equivalent: 450mm); Focus Distance: 4294967295.00m; Aperture: f/5.6; Exposure Time: 0.0008 s (1/1250); ISO equiv: 200; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Light Source: Unknown; Flash Fired: No; Orientation: Normal.